Laser machining device and laser machining method

ABSTRACT

A laser machining device  1  comprises a laser light source  10 , a spatial light modulator  20 , a controller  22 , a converging optical system  30 , and a shielding member  40 . The phase-modulating spatial light modulator  20  inputs a laser beam outputted from the laser light source  10 , displays a hologram modulating a phase of the laser beam at each of a plurality of pixels arranged two-dimensionally, and outputs the phase-modulated laser beam. The controller  22  causes the spatial light modulator  20  to display a plurality of holograms sequentially, lets the converging optical system  30  converge the laser beam outputted from the spatial light modulator  20  at converging positions having a fixed number of M, selectively places N converging positions out of the M converging positions into a machining region  91 , and machines an object to be machined  90.

TECHNICAL FIELD

The present invention relates to a device and method for machining anobject to be machined by irradiating a machining region in the objectwith a converged laser beam.

BACKGROUND ART

An object to be machined can be machined by converging a laser beamoutputted from a laser light source through a converging optical systemand irradiating the object with thus converged laser beam. The objectcan be machined into a desirable form by scanning a laser beam at asingle converging position if the laser beam is converged by using alens alone. However, it takes a long time for machining in this case.

The easiest technique for reducing the machining time is performingmultipoint simultaneous machining by emitting converged laser beams at aplurality of converging positions. The multipoint simultaneous machiningcan be carried out by using a plurality of laser light sources andconverging the respective laser beams outputted from the laser lightsources through lenses, for example. In this case, however, the use of aplurality of laser light sources increases their cost and complicatestheir installation area and optical systems.

An invention aimed at solving such a problem is disclosed in PatentLiterature 1. The invention disclosed in Patent Literature 1 causes aphase-modulating spatial light modulator to display a hologram, so as tophase-modulate a laser beam outputted from a single laser light source,and irradiates a plurality of positions simultaneously with thusphase-modulated laser beam converged through a converging opticalsystem. The hologram displayed in the spatial light modulator has such aphase modulation distribution as to converge the laser beam at aplurality of converging positions through the converging optical system.

-   Patent Literature 1: Japanese Patent Publication No. 2723798

DISCLOSURE OF INVENTION Technical Problem

In the invention disclosed in Patent Literature 1, it is desirable forlaser beams irradiating the plurality of converging positions to haveuniform energy. In this case, the energy of the laser beam irradiatingeach converging position is substantially in inverse proportion to thenumber of converging positions. For example, the energy per convergingposition of a laser beam irradiating two converging positions is halfthat irradiating a single converging position.

On the other hand, abrasion rate has been known to vary depending on thelaser light intensity when metal surfaces are machined by abrasion withfemtosecond laser beams. That is, as the number of converging positionsvaries in the invention disclosed in Patent Literature 1, the energy ofthe laser beam irradiating each converging position fluctuates, therebychanging the degree of machining at each converging position.

For solving such a problem, ND (Neutral Density) filters havingdesirable attenuation factors may be inserted according to the number ofconverging positions such that the energy of the laser beam irradiatingeach converging position is kept constant regardless of the number ofconverging positions. Replacing the ND filters each time the number ofconverging positions changes, however, will remarkably lower theefficiency.

For overcoming the problems mentioned above, it is an object of thepresent invention to provide a device and method for machining amachining region in an object to be machined by irradiating a pluralityof converging positions or a converging region having a fixed areasimultaneously with a laser beam while using a phase-modulating spatiallight modulator displaying a hologram, which can easily keep the energyof the laser beam irradiating each converging position or convergingregion substantially constant even when the number of convergingpositions or the area of the converging region varies.

Solving Means

The laser machining device in accordance with the present invention is adevice for machining an object to be machined by irradiating a machiningregion in the object with a converged laser beam, the device comprising(1) a laser light source for outputting a laser beam; (2) aphase-modulating spatial light modulator for inputting the laser beamoutputted from the laser light source, displaying a hologram modulatinga phase of the laser beam at each of a plurality of pixels arrangedtwo-dimensionally, and outputting the phase-modulated laser beam; (3) aconverging optical system disposed downstream of the spatial lightmodulator; and (4) a controller for causing the spatial light modulatorto display such a hologram that the laser beam outputted from thespatial light modulator is converged at a plurality of convergingpositions by the converging optical system. Further, the controllercauses the spatial light modulator to display a plurality of hologramssequentially and, when the laser beam outputted from the spatial lightmodulator displaying each of the plurality of holograms is fed into theconverging optical system, lets the converging optical system convergethe laser beam at converging positions having a fixed number of M,selectively places N converging positions out of the M convergingpositions into the machining region, and machines the object. Here, M isan integer of 2 or greater, and N is an integer of at least 1 but lessthan M.

In the present invention, a laser beam outputted from the spatial lightmodulator displaying each of a plurality of holograms and fed into theconverging optical system is converged by the converging optical systemat converging positions having a fixed number of M, while N convergingpositions out of the M converging positions are selectively placed inthe machining region. However, as will be explained later, a shieldingmember disposed between the converging optical system and object keepsthe remaining (M−N) converging positions from being placed in themachining region. Alternatively, a shielding member or mirror usedtogether with a 4f optical system disposed between the spatial lightmodulator and converging optical system achieves the same result.

Preferably, the laser machining device in accordance with the presentinvention further comprises a shielding member for blocking the laserbeam such that the (M−N) converging positions out of the M convergingpositions formed by the converging optical system excluding the Nconverging positions are kept from being placed in the machining region.

Preferably, in the laser machining device in accordance with the presentinvention, the number M equals the maximum number L of convergingpositions for machining a predetermined part of the object. Here, L isan integer.

Preferably, in the laser machining device in accordance with the presentinvention, the number M is greater than the maximum number L ofconverging positions for machining a predetermined part of the object,while the controller causes the spatial light modulator to display thehologram such that the (M−L) converging positions out of the Mconverging positions excluding the maximum number L of convergingpositions are always kept from being placed in the machining region.Here, L is an integer.

Preferably, in the laser machining device in accordance with the presentinvention, the controller causes the spatial light modulator to displaythe hologram such that the laser beam converged at the (M−N) or (M−L)converging positions has a variable intensity.

Preferably, the laser machining device in accordance with the presentinvention further comprises a 4f optical system, disposed between thespatial light modulator and converging optical system, including firstand second lenses and a shielding member disposed between the first andsecond lenses, while the shielding member blocks the laser beam suchthat the (M−N) converging positions out of the M converging positionsformed by the converging optical system excluding the N convergingpositions are kept from being placed in the machining region.

Preferably, the laser machining device in accordance with the presentinvention further comprises a 4f optical system, disposed between thespatial light modulator and converging optical system, including firstand second lenses and a mirror disposed between the first and secondlenses, while the mirror reflects the laser beam such that the (M−N)converging positions out of the M converging positions formed by theconverging optical system excluding the N converging positions are keptfrom being placed in the machining region.

Preferably, in the laser machining device in accordance with the presentinvention, the controller causes the spatial light modulator to displaythe hologram such that the (M−N) converging positions out of the Mconverging positions formed by the converging optical system excludingthe N converging positions are placed in a region on the outside of themachining region.

Preferably, in the laser machining device in accordance with the presentinvention, the outside region is a space above the object.

Preferably, in the laser machining device in accordance with the presentinvention, the outside region is a space flanking the object.

Preferably, in the laser machining device in accordance with the presentinvention, the object is provided with an uninfluential region kept frominfluencing the machining of the object even when irradiated with theconverged laser beam, while the controller causes the spatial lightmodulator to display the hologram such that the (M−N) convergingpositions out of the M converging positions formed by the convergingoptical system excluding the N converging positions are placed in theuninfluential region.

Preferably, the laser machining device in accordance with the presentinvention further comprises a mover for relatively moving the object,while the controller causes the spatial light modulator to sequentiallydisplay a plurality of holograms and makes the mover relatively move theobject.

The laser machining method in accordance with the present invention is amethod for machining an object to be machined by irradiating a machiningregion in the object with a converged laser beam, the method using (1) alaser light source for outputting a laser beam; (2) a phase-modulatingspatial light modulator for inputting the laser beam outputted from thelaser light source, displaying a hologram modulating a phase of thelaser beam at each of a plurality of pixels arranged two-dimensionally,and outputting the phase-modulated laser beam; (3) a converging opticalsystem disposed downstream of the spatial light modulator; and (4) acontroller for causing the spatial light modulator to display such ahologram that the laser beam outputted from the spatial light modulatoris converged at a plurality of converging positions by the convergingoptical system. Further, the controller causes the spatial lightmodulator to display a plurality of holograms sequentially and, when thelaser beam outputted from the spatial light modulator displaying each ofthe plurality of holograms is fed into the converging optical system,lets the converging optical system converge the laser beam at convergingpositions having a fixed number of M, selectively places N convergingpositions out of the M converging positions into the machining region,and machines the object. Here, M is an integer of 2 or greater, and N isan integer of at least 1 but less than M.

Preferably, the laser machining method in accordance with the presentinvention further uses a shielding member for blocking the laser beamsuch that the (M−N) converging positions out of the M convergingpositions formed by the converging optical system excluding the Nconverging positions are kept from being placed in the machining region.

Preferably, in the laser machining method in accordance with the presentinvention, the number M equals the maximum number L of convergingpositions for machining a predetermined part of the object.

Preferably, in the laser machining method in accordance with the presentinvention, the number M is greater than the maximum number L ofconverging positions for machining a predetermined part of the object,while the controller causes the spatial light modulator to display thehologram such that the (M−L) converging positions out of the Mconverging positions excluding the maximum number L of convergingpositions are always kept from being placed in the machining region.

Preferably, in the laser machining method in accordance with the presentinvention, the controller causes the spatial light modulator to displaythe hologram such that the laser beam converged at the (M−N) or (M−L)converging positions has a variable intensity.

Preferably, the laser machining method in accordance with the presentinvention further uses a 4f optical system, disposed between the spatiallight modulator and converging optical system, including first andsecond lenses and a shielding member disposed between the first andsecond lenses, while the shielding member blocks the laser beam suchthat the (M−N) converging positions out of the M converging positionsformed by the converging optical system excluding the N convergingpositions are kept from being placed in the machining region.

Preferably, the laser machining method in accordance with the presentinvention further uses a 4f optical system, disposed between the spatiallight modulator and converging optical system, including first andsecond lenses and a mirror disposed between the first and second lenses,while the mirror reflects the laser beam such that the (M−N) convergingpositions out of the M converging positions formed by the convergingoptical system excluding the N converging positions are kept from beingplaced in the machining region.

Preferably, when a laser having a high peak power such as a femtosecondlaser is used, the 4f optical system is held in a vacuum state in orderto prevent air breakdown.

Preferably, in the laser machining method in accordance with the presentinvention, the controller causes the spatial light modulator to displaythe hologram such that the (M−N) converging positions out of the Mconverging positions formed by the converging optical system excludingthe N converging positions are placed in a region on the outside of themachining region.

Preferably, in the laser machining method in accordance with the presentinvention, the outside region is a space above the object.

Preferably, in the laser machining method in accordance with the presentinvention, the outside region is a space flanking the object.

Preferably, in the laser machining method in accordance with the presentinvention, the object is provided with an uninfluential region kept frominfluencing the machining of the object even when irradiated with theconverged laser beam, while the controller causes the spatial lightmodulator to display the hologram such that the (M−N) convergingpositions out of the M converging positions formed by the convergingoptical system excluding the N converging positions are placed in theuninfluential region.

Preferably, the laser machining method in accordance with the presentinvention further uses a mover for relatively moving the object, whilethe controller causes the spatial light modulator to sequentiallydisplay a plurality of holograms and makes the mover relatively move theobject.

The laser machining device in accordance with the present invention is adevice for machining an object to be machined by irradiating a machiningregion in the object with a converged laser beam, the device comprising(1) a laser light source for outputting a laser beam; (2) aphase-modulating spatial light modulator for inputting the laser beamoutputted from the laser light source, displaying a hologram modulatinga phase of the laser beam at each of a plurality of pixels arrangedtwo-dimensionally, and outputting the phase-modulated laser beam; (3) aconverging optical system disposed downstream of the spatial lightmodulator; and (4) a controller for causing the spatial light modulatorto display such a hologram that the laser beam outputted from thespatial light modulator is converged into a predetermined convergingregion by the converging optical system. Further, the controller causesthe spatial light modulator to display a plurality of hologramssequentially and, when the laser beam outputted from the spatial lightmodulator displaying each of the plurality of holograms is fed into theconverging optical system, lets the converging optical system convergethe laser beam into a converging region having a fixed area X,selectively places a converging region having an area Y out of theconverging region having the area X into the machining region, andmachines the object. Here, X is a positive number, and Y is a positivenumber not greater than X.

In the present invention, a laser beam outputted from the spatial lightmodulator displaying each of a plurality of holograms and fed into theconverging optical system is converged by the converging optical systeminto a converging region having a fixed area X, while a convergingregion having an area Y out of the converging region having the area Xis selectively placed in the machining region. However, as will beexplained later, a shielding member disposed between the convergingoptical system and object keeps the remaining (M−N) converging positionsfrom being placed in the machining region. Alternatively, a shieldingmember or mirror used together with a 4f optical system disposed betweenthe spatial light modulator and converging optical system achieves thesame result.

Preferably, the laser machining device in accordance with the presentinvention further comprises a shielding member for blocking the laserbeam such that the converging region having the area (X−Y) out of theconverging region having the area X formed by the converging opticalsystem excluding the converging region having the area Y is kept frombeing placed in the machining region.

Preferably, in the laser machining device in accordance with the presentinvention, the area X equals the maximum area Z of the converging regionfor machining a predetermined part of the object. Here, Z is a positivenumber.

Preferably, in the laser machining device in accordance with the presentinvention, the area X is greater than the maximum area Z of theconverging region for machining a predetermined part of the object,while the controller causes the spatial light modulator to display thehologram such that the converging region having the area (X−Z) out ofthe converging region having the area X excluding the converging regionhaving the maximum area Z is always kept from being placed in themachining region. Here, Z is a positive number.

Preferably, in the laser machining device in accordance with the presentinvention, the controller causes the spatial light modulator to displaythe hologram such that the laser beam converged into the convergingregion having the area (X−Y) or (X−Z) has a variable intensity.

Preferably, the laser machining device in accordance with the presentinvention further comprises a 4f optical system, disposed between thespatial light modulator and converging optical system, including firstand second lenses and a shielding member disposed between the first andsecond lenses, while the shielding member blocks the laser beam suchthat the converging region having the area (X−Y) out of the convergingregion having the area X formed by the converging optical systemexcluding the converging region having the area Y is kept from beingplaced in the machining region.

Preferably, the laser machining device in accordance with the presentinvention further comprises a 4f optical system, disposed between thespatial light modulator and converging optical system, including firstand second lenses and a mirror disposed between the first and secondlenses, while the mirror reflects the laser beam such that theconverging region having the area (X−Y) out of the converging regionhaving the area X formed by the converging optical system excluding theconverging region having the area Y is kept from being placed in themachining region.

Preferably, in the laser machining device in accordance with the presentinvention, the controller causes the spatial light modulator to displaythe hologram such that the converging region having the area (X−Y) outof the converging region having the area X formed by the convergingoptical system excluding the converging region having the area Y isplaced in a region on the outside of the machining region.

Preferably, in the laser machining device in accordance with the presentinvention, the outside region is a space above the object.

Preferably, in the laser machining device in accordance with the presentinvention, the outside region is a space flanking the object.

Preferably, in the laser machining device in accordance with the presentinvention, the object is provided with an uninfluential region kept frominfluencing the machining of the object even when irradiated with theconverged laser beam, while the controller causes the spatial lightmodulator to display the hologram such that the converging region havingthe area (X−Y) out of the converging region having the area X formed bythe converging optical system excluding the converging region having thearea Y is placed in the uninfluential region.

Preferably, the laser machining device in accordance with the presentinvention further comprises a mover for relatively moving the object,while the controller causes the spatial light modulator to sequentiallydisplay a plurality of holograms and makes the mover relatively move theobject.

The laser machining method in accordance with the present invention is amethod for machining an object to be machined by irradiating a machiningregion in the object with a converged laser beam, the method using (1) alaser light source for outputting a laser beam; (2) a phase-modulatingspatial light modulator for inputting the laser beam outputted from thelaser light source, displaying a hologram modulating a phase of thelaser beam at each of a plurality of pixels arranged two-dimensionally,and outputting the phase-modulated laser beam; (3) a converging opticalsystem disposed downstream of the spatial light modulator; and (4) acontroller for causing the spatial light modulator to display such ahologram that the laser beam outputted from the spatial light modulatoris converged into a predetermined converging region by the convergingoptical system. Further, the controller causes the spatial lightmodulator to display a plurality of holograms sequentially and, when thelaser beam outputted from the spatial light modulator displaying each ofthe plurality of holograms is fed into the converging optical system,lets the converging optical system converge the laser beam into aconverging region having a fixed area X, selectively places a convergingregion having an area Y out of the converging region having the area Xinto the machining region, and machines the object. Here, X is apositive number, and Y is a positive number not greater than X.

Preferably, the laser machining method in accordance with the presentinvention further uses a shielding member for blocking the laser beamsuch that the converging region having the area (X−Y) out of theconverging region having the area X formed by the converging opticalsystem excluding the converging region having the area Y is kept frombeing placed in the machining region.

Preferably, in the laser machining method in accordance with the presentinvention, the area X equals the maximum area Z of the converging regionfor machining a predetermined part of the object. Here, Z is a positivenumber.

Preferably, in the laser machining method in accordance with the presentinvention, the area X is greater than the maximum area Z of theconverging region for machining a predetermined part of the object,while the controller causes the spatial light modulator to display thehologram such that the converging region having the area (X−Z) out ofthe converging region having the area X excluding the converging regionhaving the maximum area Z is always kept from being placed in themachining region. Here, Z is a positive number.

Preferably, in the laser machining method in accordance with the presentinvention, the controller causes the spatial light modulator to displaythe hologram such that the laser beam converged into the convergingregion having the area (X−Y) or (X−Z) has a variable intensity.

Preferably, the laser machining method in accordance with the presentinvention further uses a 4f optical system, disposed between the spatiallight modulator and converging optical system, including first andsecond lenses and a shielding member disposed between the first andsecond lenses, while the shielding member blocks the laser beam suchthat the converging region having the area (X−Y) out of the convergingregion having the area X formed by the converging optical systemexcluding the converging region having the area Y is kept from beingplaced in the machining region.

Preferably, the laser machining method in accordance with the presentinvention further uses a 4f optical system, disposed between the spatiallight modulator and converging optical system, including first andsecond lenses and a mirror disposed between the first and second lenses,while the mirror reflects the laser beam such that the converging regionhaving the area (X−Y) out of the converging region having the area Xformed by the converging optical system excluding the converging regionhaving the area Y is kept from being placed in the machining region.

Preferably, in the laser machining method in accordance with the presentinvention, the controller causes the spatial light modulator to displaythe hologram such that the converging region having the area (X−Y) outof the converging region having the area X formed by the convergingoptical system excluding the converging region having the area Y isplaced in a region on the outside of the machining region.

Preferably, in the laser machining method in accordance with the presentinvention, the outside region is a space above the object.

Preferably, in the laser machining method in accordance with the presentinvention, the outside region is a space flanking the object.

Preferably, in the laser machining method in accordance with the presentinvention, the object is provided with an uninfluential region kept frominfluencing the machining of the object even when irradiated with theconverged laser beam, while the controller causes the spatial lightmodulator to display the hologram such that the converging region havingthe area (X−Y) out of the converging region having the area X formed bythe converging optical system excluding the converging region having thearea Y is placed in the uninfluential region.

Preferably, the laser machining method in accordance with the presentinvention further uses a mover for relatively moving the object, whilethe controller causes the spatial light modulator to sequentiallydisplay a plurality of holograms and makes the mover relatively move theobject.

Effects of Invention

The laser machining device or method in accordance with the presentinvention can machine a machining region in an object to be machined byirradiating a plurality of converging positions or a converging regionhaving a fixed area simultaneously with a laser beam while using aphase-modulating spatial light modulator displaying a hologram, and caneasily keep the energy of the laser beam irradiating each convergingposition or converging region substantially constant even when thenumber of converging positions or the area of the converging regionvaries.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a diagram illustrating a laser machining device 1 inaccordance with a first embodiment;

FIG. 2 is a diagram explaining a first mode in which a controller 22causes a driver 21 to write a hologram into a spatial light modulator 20in the laser machining device 1 in accordance with the first embodiment;

FIG. 3 is a diagram explaining a second mode in which the controller 22causes the driver 21 to write a hologram into the spatial lightmodulator 20 in the laser machining device 1 in accordance with thefirst embodiment;

FIG. 4 is a diagram explaining a third mode in which the controller 22causes the driver 21 to write a hologram into the spatial light,modulator 20 in the laser machining device 1 in accordance with thefirst embodiment;

FIG. 5 is a diagram explaining a laser machining method of a comparativeexample in the description of the first embodiment;

FIG. 6 is a diagram explaining a first mode of the laser machiningmethod in accordance with the first embodiment;

FIG. 7 is a diagram explaining a second mode of the laser machiningmethod in accordance with the first embodiment;

FIG. 8 is a diagram explaining a third mode of the laser machiningmethod in accordance with the first embodiment;

FIG. 9 is a diagram explaining a fourth mode of the laser machiningmethod in accordance with the first embodiment;

FIG. 10 is a flowchart of a hologram producing method in the firstembodiment;

FIG. 11 is a flowchart of a hologram modifying method in the firstembodiment;

FIG. 12 is a diagram illustrating the relationship among a convergingoptical system 30, a shielding member 40, an object to be machined 90,and converging positions in the laser machining device 1 in accordancewith the first embodiment and the laser machining method in accordancewith the first embodiment;

FIG. 13 is a diagram illustrating the structure of a laser machiningdevice 2 in accordance with a second embodiment;

FIG. 14 is a diagram illustrating the structure of a laser machiningdevice 3 in accordance with a third embodiment;

FIG. 15 is a diagram illustrating a part of the structure of a lasermachining device in accordance with a fourth embodiment;

FIG. 16 is a diagram illustrating the structure of a laser machiningdevice 5 in accordance with a fifth embodiment;

FIG. 17 is a diagram explaining a laser machining method in accordancewith the fifth embodiment;

FIG. 18 is a diagram illustrating respective arrangements of laser beamconverging positions in a machining region 91 and a shielded region 92in Example 1;

FIG. 19 is a chart listing laser beam intensities at respectiveconverging positions in a comparative example in the description ofExample 1;

FIG. 20 is a chart listing laser beam intensities at respectiveconverging positions in Example 1;

FIG. 21 is a plan view of Y-branched optical waveguides;

FIG. 22 is a diagram explaining a method of forming Y-branched opticalwaveguides of a comparative example in the description of Example 3;

FIG. 23 is a diagram explaining a method of forming Y-branched opticalwaveguides of Example 3;

FIG. 24 is a diagram explaining another way of the first mode of thelaser machining method in accordance with the first embodiment;

FIG. 25 is a diagram explaining still another way of the first mode ofthe laser machining method in accordance with the first embodiment;

FIG. 26 is a diagram illustrating a part of the structure of the lasermachining device in accordance with the fourth embodiment;

FIG. 27 is a diagram illustrating a part of the structure of the lasermachining device in accordance with the fourth embodiment;

FIG. 28 is a diagram illustrating a part of the structure of the lasermachining device in accordance with another mode of the fourthembodiment;

FIG. 29 is a diagram illustrating a part of the structure of the lasermachining device in accordance with still another mode of the fourthembodiment;

FIG. 30 is a diagram explaining a laser machining method in accordancewith a sixth embodiment;

FIG. 31 is a diagram illustrating respective arrangements of laser beamconverging positions in the machining region 91 and shielded region 92in Example 2; and

FIG. 32 is a chart listing laser beam intensities at respectiveconverging positions in Example 2.

REFERENCE SIGNS LIST

1 to 5 . . . laser machining device; 10 . . . laser light source; 11 . .. spatial filter; 12 . . . collimator lens; 13, 14 . . . mirror; 20 . .. spatial light modulator; 21 . . . driver; 22 . . . controller; 30 . .. converging optical system; 40 . . . shielding member; 50 . . . 4 foptical system; 51, 52 . . . lens; 53 . . . shielding member; 54 . . .mirror; 55 . . . damper; 60 . . . mover; 90 . . . object to be machined;91 . . . machining region

DESCRIPTION OF EMBODIMENTS

In the following, the best modes for carrying out the present inventionwill be explained in detail with reference to the accompanying drawings.In the explanation of the drawings, the same constituents will bereferred to with the same signs while omitting their overlappingdescriptions.

First Embodiment Structure of a Laser Machining Device 1

To begin with, a first embodiment of the laser machining device andmethod in accordance with the present invention will be explained. FIG.1 is a diagram illustrating the structure of the laser machining device1 in accordance with the first embodiment. The laser machining device 1illustrated in this drawing, which is a device for machining an objectto be machined 90 by irradiating a machining region in the object 90with a converged laser beam, comprises a laser light source 10, aspatial filter 11, a collimator lens 12, mirrors 13, 14, a spatial lightmodulator 20, a driver 21, a controller 22, a converging optical system30, and a shielding member 40.

The laser light source 10, which outputs a laser beam for irradiatingthe machining region 91 of the object 90, is preferably a pulsed lasersource such as a femtosecond laser light source or Nd:YAG laser lightsource. The laser beam outputted from the laser light source 10 istransmitted through the spatial filter 11, collimated by the collimatorlens 12, and reflected by the mirrors 13, 14, so as to be fed into thespatial light modulator 20.

The spatial light modulator 20, which is of phase modulation type,inputs the laser beam outputted from the laser light source 10, displaysa hologram modulating a phase of the laser beam at each of a pluralityof pixels arranged two-dimensionally, and outputs the phase-modulatedlaser beam. The phase hologram displayed by the spatial light modulator20 is preferably a hologram (CGH: Computer Generated Hologram) obtainedby numerical computing.

The spatial light modulator 20 is any of reflection and transmissiontypes. The spatial light modulator 20 of reflection type may be any ofLCOS (Liquid Crystal on Silicon), MEM (Micro Electro MechanicalSystems), and light-addressable types. The spatial light modulator 20 oftransmission type may be an LCD (Liquid Crystal Display) and the like.FIG. 1 illustrates the spatial light modulator 20 of reflection type.

The driver 21, which sets the amount of phase modulation at each of aplurality of pixels arranged two-dimensionally in the spatial lightmodulator 20, provides the spatial light modulator 20 with a signal forsetting the amount of phase modulation for each pixel. The driver 21sets the amount of phase modulation at each of a plurality of pixelsarranged two-dimensionally in the spatial light modulator 20, therebycausing the spatial light modulator 20 to display a hologram.

The converging optical system 30, which is disposed downstream of thespatial light modulator 20, inputs the laser beam outputted from thespatial light modulator 20 after being phase-modulated per pixeltherein. In particular, the converging optical system 30 includes a lensfor Fourier-transforming the laser beam outputted from the spatial lightmodulator 20. Thus Fourier-transformed image is formed on the back focalplane of the Fourier-transforming lens.

The controller 22, which is constructed by a computer, for example,controls the operation of the driver 21, thereby causing the driver 21to write a hologram into the spatial light modulator 20. Here, thecontroller 22 causes the spatial light modulator 20 to display ahologram by which the laser beam outputted from the spatial lightmodulator 20 is converged at a plurality of converging positions throughthe converging optical system 30.

In particular, the controller 22 causes the spatial light modulator 20to display a plurality of holograms sequentially in this embodiment.Then, the controller 22 lets the converging optical system 30 convergethe laser beam outputted from the spatial light modulator 20 displayingeach of a plurality of holograms at converging positions having a fixednumber of M, selectively places N converging positions out of the Mconverging positions into the machining region 91, and machines theobject 90. Here, M is an integer of 2 or greater, and N is an integer ofat least 1 but less than M. The machining region 91 where the Nconverging positions are placed includes not only the front face of theobject 90 but also the inside thereof.

The shielding member 40 blocks the laser beam such that the (M−N)converging positions out of the M converging positions formed by theconverging optical system 30 excluding the N converging positions arekept from being placed in the machining region 90.

FIGS. 2 to 4 are diagrams explaining respective modes in which thecontroller 22 causes the driver 21 to write a hologram into the spatiallight modulator 20 in the laser machining device 1 in accordance withthe first embodiment.

In the first mode illustrated in FIG. 2, the controller 22 includes acentral processing unit 221, a communicator 222, and a memory 223. Thecentral processing unit 221 prepares data for a plurality of hologramsCGH1 to CGH3 to be displayed by the spatial light modulator 20 andstores them in the memory 223. When letting the spatial light modulator20 display a hologram, the central processing unit 221 reads the datafor the hologram from the memory 223 and sends thus read hologram datato the communicator 222, and the communicator 222 transmits the hologramdata to the processor 211 of the driver 21. The processor 211 of thedriver 21 sends the hologram data received from the controller 22 to thespatial light modulator 20 and causes the spatial light modulator 20 todisplay the hologram.

In the second mode illustrated in FIG. 3, a memory 213 of the driver 21stores data for a plurality of holograms CGH1 to CGH3 to be displayed bythe spatial light modulator 20. When letting the spatial light modulator20 display a hologram, the controller 22 designates hologram data storedin the memory 213 for the driver 21, causes the latter to send thehologram data to the spatial light modulator 20, and makes the spatiallight modulator 20 display the hologram.

In the third mode illustrated in FIG. 4, the memory 223 included in thecontroller 22 stores data for desirable patterns 1 to 3 of convergingpositions for converging the laser beam through the converging opticalsystem 30. When letting the spatial light modulator 20 display ahologram, the central processing unit 221 reads the data for a desirablepattern from the memory 223, creates a hologram which can reproduce thusread desirable pattern, and sends the data for this hologram to thecommunicator 222, while the communicator 222 transmits the hologram datato the processor 211 of the driver 21. Then, the processor 211 of thedriver 21 sends the hologram data received from the controller 22 to thespatial light modulator 20 and causes the spatial light modulator 20 todisplay the hologram.

Any of the modes illustrated in FIGS. 2 to 4 may create a hologram froma desirable pattern of converging positions according to any oftechniques of Fourier transform and Fresnel zone plate types. TheFourier transform type can form the hologram by an algorithm such as aGS method, while the Fresnel zone plate type can form the hologram by analgorithm such as an ORA (optimal-rotation-angle) method.

The GS method is described in R. W. Gerchberg and W. O. Saxton, “Apractical algorithm for the determination of phase from image anddiffraction plane pictures”, Optik, Vol. 35, pp. 237-246 (1972). The ORAmethod is described in Jorgen Bengtsson, “Kinoform design with anoptimal-rotation-angle method”, Applied Optics, Vol. 33, no. 29, pp.6879-6884 (1994).

Laser Machining Method

The operation of the laser machining device 1 in accordance with thefirst embodiment and the laser machining method in accordance with thefirst embodiment will now be explained in comparison with a comparativeexample. Here, the machining region 91 of the object 90 is irradiatedwith a converged laser beam, so as to machine the object 90 such thatthree alphabetical letters of “H”, “P”, and “K” are displayed in amultipoint scheme.

Laser Machining Method: Comparative Example

FIG. 5 is a diagram explaining a laser machining method of a comparativeexample. In each of (a) to (c) in this diagram, circles indicaterespective laser beam converging positions. FIG. 5( a) illustrates howthe laser beam irradiates 12 converging positions in order to machineletter “H”. FIG. 5( b) illustrates how the laser beam irradiates 11converging positions in order to machine letter “P”. FIG. 5( c)illustrates how the laser beam irradiates 10 converging positions inorder to machine letter “K”.

In this comparative example, respective holograms adapted to machineletters “H”, “P”, and “K” are sequentially displayed in the spatiallight modulator. When thus machining “H”, “P”, and “K” one by one inthis order, the number of laser beam converging positions varies amongthe letters, so that the laser beam irradiation energy at eachconverging position differs from letter to letter, thereby causingfluctuations in machining depending on the letters.

In this embodiment, by contrast, the laser beam displaying each of aplurality of holograms outputted from the spatial light modulator 20 isconverged by the converging optical system 30 at converging positionshaving a fixed number of M, while N converging positions out of the Mconverging positions are selectively placed in the machining region 91,and the object 90 is machined. The shielding member 40 keeps theremaining (M−N) converging positions from being placed in the object 90.

Laser Machining Method: First Mode

FIG. 6 is a diagram explaining the first mode of the laser machiningmethod in accordance with the first embodiment. FIG. 6( a) illustrateshow the laser beam irradiates 12 converging positions in order tomachine letter “H”. FIG. 6( b) illustrates how the laser beam irradiates11 converging positions within the machining region 91 in order tomachine letter “P” and 1 converging position on the shielding member 40.FIG. 6( c) illustrates how the laser beam irradiates 10 convergingpositions within the machining region 91 in order to machine letter “K”and 2 converging positions on the shielding member 40.

That is, in the first mode, the laser beam outputted from the spatiallight modulator 20 sequentially displaying the respective hologramscorresponding to “H”, “P”, and “K” is converged by the convergingoptical system 30 at 12 (M) converging positions having a fixed number.When machining letter “H”, all of the 12 (M) converging positions areselectively placed in the machining region 91, so as to machine theobject 90 (FIG. 6( a)). When machining letter “P”, 11 (N) convergingpositions out of the 12 (M) converging positions are selectively placedin the machining region 91, so as to machine the object 90 (FIG. 6( b)).When machining letter “K”, 10 (N) converging positions out of the 12 (M)converging positions are selectively placed in the machining region 91,so as to machine the object 90 (FIG. 6( c)). In FIG. 6, the maximumnumber L of converging positions for machining the letter “H” part ofthe object 90 (the part having the greatest number of convergingpositions required for machining among letters “H”, “P”, and “K” andcorresponding to the “predetermined part” in the claims) is 12, whichequals the total of laser beam converging positions M. Here, L is aninteger.

Thus, even when letters are machined one by one in the order of “H”,“P”, and “K”, the number of laser beam converging positions is fixed at12 regardless of the letters, so that the laser beam irradiation energyat each converging position is substantially constant among the letters,whereby fluctuations in machining can be suppressed independently of theletters.

Laser Machining Method: Another Way of the First Mode

FIG. 24 is a diagram explaining another way of the above-mentioned firstmode. This is the same as the first mode explained with reference toFIG. 6 until the laser beam for machining letter “K” irradiates 10converging positions within the machining region 91, but differstherefrom in that the laser beam irradiates only 1 converging positionon the shielding member 40. Here, the intensity of the laser beamirradiating each converging position on the shielding member 40 varies,for example, such that the intensity of the laser beam irradiating thesingle converging position on the shielding member 40 in FIG. 24( c) isabout twice that irradiating each of the 2 converging positions on theshielding member 40 in FIG. 6( c). That is, the intensity of the laserbeam irradiating the converging positions on the shielding member 40 isvariable. For convenience of explanation, the intensity of laser beamsis expressed in proportion to the size of white circles in FIG. 24 (asin FIG. 25 which will be explained later). Such CGH with differentintensities can be made by varying amplitudes of target patterns in theGS method, for example.

The intensity of the laser beam irradiating the shielding member 40 maynot only be raised but lowered as illustrated in FIG. 25( c). This isdone in order to prevent the intensity of the laser beam from becomingso high as to machine the shielding member 40. FIG. 25 is a diagramexplaining still another way of the first mode, which differs from thefirst mode of FIG. 6 in that the laser beam irradiates 4 convergingpositions on the shielding member 40 in FIG. 25( c). Here, the intensityof the laser beam irradiating each of 4 converging positions on theshielding member 40 in FIG. 25( c) is about 0.5 times that of the laserbeam irradiating each of 2 converging positions on the shielding member40 in FIG. 6( c) and lower than a threshold at which the shieldingmember 40 is machined.

Laser Machining Method: Second Mode

FIG. 7 is a diagram explaining the second mode of the laser machiningmethod in accordance with the first embodiment. FIG. 7( a) illustrateshow the laser beam irradiates 12 converging positions within themachining region 91 in order to machine letter “H” and 3 convergingpositions on the shielding member 40. FIG. 7( b) illustrates how thelaser beam irradiates 11 converging positions within the machiningregion 91 in order to machine letter “P” and 4 converging positions onthe shielding member 40. FIG. 7( c) illustrates how the laser beamirradiates 10 converging positions within the machining region 91 inorder to machine letter “K” and 5 converging position on the shieldingmember 40.

That is, in the second mode, the laser beam outputted from the spatiallight modulator 20 sequentially displaying the respective hologramscorresponding to “H”, “P”, and “K” is converged by the convergingoptical system 30 at 15 (M) converging positions having a fixed number.When machining letter “H”, 12 (N) converging positions out of the 15 (M)converging positions are selectively placed in the machining region 91,so as to machine the object 90 (FIG. 7( a)). When machining letter “P”,11 (N) converging positions out of the 15 (M) converging positions areselectively placed in the machining region 91, so as to machine theobject 90 (FIG. 7( b)). When machining letter “K”, 10 (N) convergingpositions out of the 15 (M) converging positions are selectively placedin the machining region 91, so as to machine the object 90 (FIG. 7( c)).

Thus, even when letters are machined one by one in the order of “H”,“P”, and “K”, the number of laser beam converging positions is fixed at15 regardless of the letters, so that the laser beam irradiation energyat each converging position is substantially constant among the letters,whereby fluctuations in machining can be suppressed independently of theletters.

In the first mode of the laser machining method illustrated in FIG. 6,the number (M) of converging positions formed by the converging opticalsystem 30 is the maximum number (L) required for machining each ofletters “H”, “P”, and “K”. That is, M=L. In the second mode of the lasermachining method illustrated in FIG. 7, by contrast, the number (M) ofconverging positions formed by the converging optical system 30 is 15that is greater than the above-mentioned maximum number 12 (L). That is,M>L. In the second mode, the controller 22 causes the spatial lightmodulator 20 to display holograms such that 3 converging positions outof the M (15) converging positions excluding the maximum number L (12)are always kept from being placed in the machining region 91, i.e., areplaced on the shielding member 40. The second mode is favorable in that,when the intensity of the laser beam outputted from the laser lightsource 10 is high, the number M of converging positions formed by eachhologram (i.e., the magnitude of laser beam irradiation energy at eachconverging position) can be set appropriately. In either mode, whenmachining letters “H”, “P”, and “K”, the number of laser beam convergingpositions is fixed regardless of the letters, whereby the laser beamirradiation energy at each converging position is substantially constantamong the letters.

Laser Machining Method: Third Mode

FIG. 8 is a diagram explaining the third mode of the laser machiningmethod in accordance with the first embodiment. In each of (a) to (c) inthis diagram, white circles indicate respective laser beam convergingpositions, while black circles represent already machined positions.Here, the machining region 91 of the object 90 is irradiated with aconverged laser beam so as to machine the object 90 such that threealphabetical letters of “H”, “T”, and “V” are displayed in a multipointscheme. Letters “H”, “T”, and “V” are not machined one by one in thisorder, but each of “H” and “T” is partly machined at first, then theremaining part of each of “H” and “T” is machined, and finally the wholeletter “V” is machined.

In the third mode, the laser beam outputted from the spatial lightmodulator 20 sequentially displaying 3 holograms is converged by theconverging optical system 30 at 14 converging positions having a fixednumber. When partly machining each of letters “H” and “T”, 8 convergingpositions out of the 14 converging positions are selectively placed inthe machining region 91, so as to machine the object 90, while theremaining 6 converging positions are placed on the shielding member 40(FIG. 8( a)). When machining the remaining part of each of letters “H”and “T”, 12 converging positions out of the 14 converging positions areselectively placed in the machining region 91, so as to machine theobject 90, while the remaining 2 converging positions are placed on theshielding member 40 (FIG. 8( b)). When machining letter “V”, 9converging positions out of the 14 converging positions are selectivelyplaced in the machining region 91, so as to machine the object 90, whilethe remaining 5 converging positions are placed on the shielding member40 (FIG. 8( c)).

Thus, even when letters “H”, “T”, and “V” are not machined one by one inthis order but in a predetermined order, the number of laser beamconverging positions is fixed at 14 regardless of the letters, so thatthe laser beam irradiation energy at each converging position issubstantially constant among the letters, whereby fluctuations inmachining can be suppressed independently of the letters. The third modecan appropriately set the number of converging positions formed by eachhologram (i.e., the magnitude of laser beam irradiation energy at eachconverging position) according to the intensity of the laser beamoutputted from the laser light source 10 independently of letters to bemachined.

Laser Machining Method: Fourth Mode

FIG. 9 is a diagram explaining the fourth mode of the laser machiningmethod in accordance with the first embodiment. In each of (a) to (c) inthis diagram, white circles indicate respective laser beam convergingpositions, while black circles represent already machined positions.Here, the machining region 91 of the object 90 is irradiated with aconverged laser beam so as to machine the object 90 such that a singlealphabetical letter of “H” is displayed in a multipoint scheme. A partof letter “H” is machined at first, then another part thereof ismachined, and finally the remaining part thereof is machined.

In the fourth mode, the laser beam outputted from the spatial lightmodulator 20 sequentially displaying 3 holograms is converged by theconverging optical system 30 at 8 converging positions having a fixednumber. When machining a part of letter “H”, 6 converging positions outof the 8 converging positions are selectively placed in the machiningregion 91, so as to machine the object 90, while the remaining 2converging positions are placed on the shielding member 40 (FIG. 9( a)).When machining another part of letter “H”, all of the 8 convergingpositions are selectively placed in the machining region 91, so as tomachine the object 90 (FIG. 9( b)). When machining the remaining part ofletter “H”, 3 converging positions out of the 8 converging positions areselectively placed in the machining region 91, so as to machine theobject 90, while the remaining 5 converging positions are placed on theshielding member 40 (FIG. 9( c)).

Thus, even when machining a single letter of “H” in 3 sessions, thenumber of laser beam converging positions in each session is fixed at 8,whereby fluctuations in machining in each session can be suppressed. Thefourth mode can also appropriately set the number of convergingpositions formed by each hologram (i.e., the magnitude of laser beamirradiation energy at each converging position) according to theintensity of the laser beam outputted from the laser light source 10independently of letters to be machined.

Hologram Producing Method

A hologram producing method in the laser machining device 1 inaccordance with the first embodiment and the laser machining method inaccordance with the first embodiment will now be explained. FIG. 10 is aflowchart of a hologram producing method in the first embodiment.

When no machining plan in each session has been determined yet (“No” instep S11), the maximum machining point number that is the largest numberof laser beam converging positions in the machining region 91 in eachmachining session is determined (step S12), and then the flow shifts tostep S16. When a machining plan in each session has already beendetermined (“Yes” in step S11) while the maximum machining point numberhas already been known (“Yes” in step S13), the flow shifts to step S16.

When a machining plan in each session has already been determined (“Yes”in step S11) while the maximum machining point number has not been known(“No” in step S13), it is determined that there is no unnecessary lightconverged on the shielding member 40, the maximum machining point numberthat is the largest number of laser beam converging positions in themachining region 91 in each machining session is found (step S14) and,if the laser beam intensity is unproblematic at each converging positionin the case employing the maximum machining point number (“Yes” in stepS15), the flow shifts to step S16. If the laser beam intensity has aproblem in that it is too high or too low at each converging position inthe case employing the maximum machining point number (“No” in stepS15), the maximum machining point number is changed (step S17), and thenthe flow shifts to step S16.

In step S16, a desirable pattern is set according to the maximummachining point number (i.e., the total number of laser beam convergingpositions in each machining session), and a computer-generated hologramis produced by using the GS or ORA method. Converging positionsreproduced by this hologram include those converged into the machiningregion 91 and, when necessary, those converged onto the shielding member40.

Hologram Modifying Method

When the spatial light modulator 20 is caused to display each of thusproduced holograms, so that the phase-modulated laser beam outputtedfrom the spatial light modulator 20 is converged at M convergingpositions through the converging optical system 30, the laser beamintensity may not be constant at each converging position in practice.In such a case, the hologram produced as mentioned above must bemodified by performing feedback on the hologram produced as mentionedabove. FIG. 11 is a flowchart of a hologram modifying method in thefirst embodiment.

For modifying a hologram, the spatial light modulator 20 is caused todisplay the hologram, and the phase-modulated laser beam outputted fromthe spatial light modulator 20 is converged by the converging opticalsystem 30 at a plurality of converging positions (step S21), and theintensity of the laser beam at each converging position is measured by aCCD (Charged Coupled Device) (step S22). When the measured intensity ofthe laser beam at each converging position is as desired (“Yes” in stepS23), the method is terminated. When the measured intensity of the laserbeam at each converging position is not as desired (“No” in step S23),on the other hand, an intensity I_(base) of a given base point in themeasured converging positions is determined (step S24), the amplitude ofthe laser beam to be reproduced at each converging position in thedesirable pattern is changed in conformity to this intensity (step S25),and a computer-generated hologram is produced again (step S26).

The intensity of the laser beam at each converging position measured instep S22 is defined as I_(n). In step S25, the ratio I_(n)/I_(base)) ofthe intensity I_(n) at each converging position to the intensityI_(base) of the base point determined in step S24 is obtained, and thegradation t_(n) of each point after the modification is determined bythe equation t_(n)=t_(base)(I_(base)/I_(n))^(1/2), where t_(base) is thegradation of the point employed as the base in the original pattern.Then, in step S26, a computer-generated hologram is produced again bythe GS method according to the gradation t_(n) of each point after themodification.

Feedback in the ORA method is described in Hidetomo Takahashi, SatoshiHasegawa, and Yoshio Hayasaki, “Holographic femtosecond laser processingusing optimal-rotation-angle method with compensation of spatialfrequency response of liquid crystal spatial frequency response ofliquid crystal spatial light modulator.” Applied Optics, Vol. 46, Issue23, pp. 5917-5923.

Such a modification of the hologram by feedback can also be employedwhen intentionally making the laser beam intensity uneven at the laserbeam converging positions in the machining region 91 in machiningsessions.

When machining the inside of the object 90 in the laser machining device1 in accordance with the first embodiment and the laser machining methodin accordance with the first embodiment, a part of the laser beamconverged by the converging optical system 30 toward a convergingposition may be blocked by the shielding member 40 as illustrated inFIG. 12. Such a state is likely to occur when an objective lens having alarge NA is used as the converging optical system 30 or when theconverging position is located deeper within the object 90. When such astate occurs, the intensity of the laser beam at the converging positiondecreases, and there is a danger of destroying the shielding member 40.For evading such a state, it is preferred to employ any of structures ofthe second to fourth embodiments which will be explained hereinafter.

Second Embodiment

The second embodiment of the laser machining device and method inaccordance with the present invention will now be explained. FIG. 13 isa diagram illustrating the structure of a laser machining device 2 inaccordance with the second embodiment. The laser machining device 2 inaccordance with the second embodiment illustrated in FIG. 13 differsfrom the structure of the laser machining device 1 in accordance withthe first embodiment illustrated in FIG. 1 in that it comprises lenses51, 52 and a shielding member 53 instead of the shielding member 40.

The lenses 51, 52 are disposed between the spatial light modulator 20and converging optical system 30 and constitute a 4f optical system 53.The shielding member 53 is disposed between the first and second lenses51, 52. The shielding member 53 blocks the laser beam such that (M−N)converging positions out of M converging positions formed by theconverging optical system 30 excluding N converging positions to beplaced in the machining region 91 are kept from being placed in themachining region 91.

This structure can lower the possibility of blocking a part of the laserbeam reaching the N converging positions to be placed in the machiningregion 91, since the shielding member 53 within the 4f optical systemcan block unnecessary light (light excluding the laser beam to reach themachining region 91). Making the NA of the lenses 51, 52 in the 4foptical system 50 greater than that of the converging optical system 30can increase the converging spot diameter in the shielding member 53.This can lower the power density in the shielding member 53, therebypreventing the shielding member 53 from being destroyed.

The laser beam outputted from the spatial light modulator 20 displayingeach of a plurality of holograms is converged by the converging opticalsystem 30 at M converging positions having a fixed number, N convergingpositions out of the M converging positions are selectively placed inthe machining region 91, and the object 90 is machined in thisembodiment as well. The shielding member 53 keeps the remaining (M−N)converging positions from being placed on the object 90. Since thenumber of laser beam converging positions is fixed at M in each session,the laser beam irradiation energy at each converging position issubstantially constant among sessions, whereby fluctuations in machiningcan be suppressed among sessions.

Third Embodiment

The third embodiment of the laser machining device and method inaccordance with the present invention will now be explained. FIG. 14 isa diagram illustrating the structure of a laser machining device 3 inaccordance with the third embodiment. The laser machining device 3 inaccordance with the third embodiment illustrated in FIG. 14 differs fromthe structure of the laser machining device 2 in accordance with thesecond embodiment illustrated in FIG. 13 in that it comprises a mirror54 and a damper 55 instead of the shielding member 53.

The mirror 54 is disposed between the first and second lenses 51, 52constituting the 4f optical system 50. The mirror 54 reflects the laserbeam such that (M−N) converging positions out of M converging positionsformed by the converging optical system 30 excluding N convergingpositions to be placed in the machining region 91 are kept from beingplaced in the machining region 91. The damper 55 is adapted to input andabsorb the laser beam reflected by the mirror 54.

This structure can lower the power density of the unnecessary lightreaching the damper 55 after being reflected by the mirror 54 (the lightexcluding the laser beam to reach the machining region 91), therebypreventing the unnecessary light from machining the shielding member andfilters.

The laser beam outputted from the spatial light modulator 20 displayingeach of a plurality of holograms is converged by the converging opticalsystem 30 at M converging positions having a fixed number, N convergingpositions out of the M converging positions are selectively placed inthe machining region 91, and the object 90 is machined in thisembodiment as well. The mirror 54 keeps the remaining (M−N) convergingpositions from being placed on the object 90. Since the number of laserbeam converging positions is fixed at M in each session, the laser beamirradiation energy at each converging position is substantially constantamong sessions, whereby fluctuations in machining can be suppressedamong sessions.

Fourth Embodiment

The fourth embodiment of the laser machining device and method inaccordance with the present invention will now be explained. FIG. 15 isa diagram illustrating a part of the structure of the laser machiningdevice in accordance with the fourth embodiment. The overall structureof the laser machining device in accordance with the fourth embodimentis substantially the same as that illustrated in FIG. 1.

In the fourth embodiment, through the driver 21, the controller 22causes the spatial light modulator 20 to display a hologram such that Nconverging positions out of M converging positions formed by theconverging optical system 30 are placed in the machining region 91,while the remaining (M−N) converging positions are placed in a region onthe outside of the machining region 91. The region on the outside of themachining region 91 is a space on the outside of the object 90.

FIG. 15 illustrates the case where the outside region mentioned above isa space above the machining region 91. As illustrated in FIG. 15, thelaser beam is converged at a converging position P₁ in the machiningregion 91 in the object 90 and machines the converging position P₁.While the laser beam is also converged at a converging position P₂ in aspace above the object 90, it does not contribute to machining theobject 90. In FIG. 15, the intensity of the laser beam (unnecessarylight) at the converging position P₂ may be either higher or lower thana machining threshold for the object 90 but is required to be such as tokeep the object 90 and other instruments within or on the outside of themachining device from being affected thereby.

FIGS. 26 and 27 illustrate cases where the outside region is a spaceflanking the machining region. As illustrated in FIGS. 26 and 27, thelaser beam is converged at the first converging position P₁ in themachining region 91 in the object 90 and machines this convergingposition P₁. While the laser beam is also converged at the secondconverging position P₂ in a space flanking the object 90, it does notcontribute to machining the object 90. The converging positions P₁, P₂may exist on the same plane (i.e., H₁ equals H₂) as illustrated in FIG.26 or different planes (i.e., H₁ and H₃ differ from each other) asillustrated in FIG. 27. Here, H₁, H₂, H₃, and the like indicate heightsfrom the bottom face of the object 90.

In FIGS. 26 and 27, the intensity of the laser beam (unnecessary light)at the converging position P₂ may be either higher or lower than amachining threshold for the object 90 but is required to be such as tokeep the object 90 and other instruments within or on the outside of themachining device from being affected thereby. The controller 22 arrangesunnecessary light as such by causing the spatial light modulator 20 todisplay a hologram as a matter of course.

The laser beam outputted from the spatial light modulator 20 displayingeach of a plurality of holograms is converged by the converging opticalsystem 30 at M converging positions having a fixed number, N convergingpositions out of the M converging positions are selectively placed inthe machining region 91, and the object 90 is machined in thisembodiment as well. The remaining (M−N) converging positions are keptfrom being placed on the object 90. Since the number of laser beamconverging positions is fixed at M in each session, the laser beamirradiation energy at each converging position is substantially constantamong sessions, whereby fluctuations in machining can be suppressedamong sessions.

Another Mode of the Fourth Embodiment

Though the arrangement of unnecessary light in the outside region (apart above or flanking the object 90) unrelated to the machining of theobject 90 is explained in the foregoing, an uninfluential region(hereinafter referred to as “uninfluential region A”) disposed withinthe object 90 and kept from influencing the machining of the object 90even when irradiated with the converged laser beam can be used as alocation where the unnecessary light is placed.

FIGS. 28 and 29 illustrate states where the uninfluential region A isdisposed within the object 90. As illustrated in FIGS. 28 and 29, thelaser beam is converged at the converging position P₁ in the machiningregion 91 in the object 90 and machines this converging position P₁.While the laser beam is also converged at the converging position P₂ inthe uninfluential region A disposed within the object 90 and machinesthis converging position P₂, this does not contribute to machining theobject 90 as a whole. The converging positions P₁, P₂ may exist on thesame plane (i.e., H₁ equals H₄) as illustrated in FIG. 28 ormultidimensional planes (i.e., H₁ and H₅ differ from each other) asillustrated in FIG. 29. Here, H₁, H₄, H₅, and the like indicate heightsfrom the bottom face of the object 90. In other words, the uninfluentialregion A may be disposed on the same plane as the converging position P₁to be machined or on a plane different therefrom. After the machining iscompleted, the uninfluential region A may be cut off and discarded asappropriate.

In FIGS. 28 and 29, the intensity of the laser beam (unnecessary light)at the converging position P₂ may be either higher or lower than amachining threshold for the object 90 but is required to be such as tokeep the part of the object 90 excluding the uninfluential region A frombeing affected thereby. The controller 22 arranges unnecessary light assuch by causing the spatial light modulator 20 to display a hologram asa matter of course.

Fifth Embodiment

The fifth embodiment of the laser machining device and method inaccordance with the present invention will now be explained. FIG. 16 isa diagram illustrating the structure of a laser machining device 5 inaccordance with the fifth embodiment. The laser machining device 5 inaccordance with the fifth embodiment illustrated in FIG. 16 differs fromthe structure of the laser machining device 1 in accordance with thefirst embodiment illustrated in FIG. 1 in that it further comprises amover 60.

The mover 60 relatively moves the object 90. Preferably, the movingdirection is perpendicular to the optical axis of the converging opticalsystem 30. Through the driver 21, the controller 22 causes the spatiallight modulator 20 to display a plurality of holograms sequentially andmakes the mover 60 move the object 90 relatively.

The operation of the laser machining device 5 in accordance with thefifth embodiment and the laser machining method in accordance with thefifth embodiment will now be explained. FIG. 17 is a diagram explainingthe laser machining device in accordance with the fifth embodiment. Ineach of (a) to (c) in this diagram, white circles indicate respectivelaser beam converging positions, while black circles represent alreadymachined positions. The object 90 is assumed to move rightward as themachining progresses from (a) to (c) in the diagram.

In this example, the laser beam outputted from the spatial lightmodulator 20 sequentially displaying 3 holograms is converged by theconverging optical system 30 at 9 converging positions having a fixednumber. In FIG. 17( a), 2 converging positions out of the 9 convergingpositions are selectively placed in the machining region 91, so as tomachine the object 90, while the remaining 7 converging positions areplaced on the shielding member 40. In FIG. 17( b) illustrating theobject 90 shifted rightward from that in FIG. 17( a) by a predetermineddistance, all of the 9 converging positions are selectively placed inthe machining region 91, so as to machine the object 90. In FIG. 17( c)illustrating the object 90 further shifted rightward from that in FIG.17( b) by a predetermined distance, 2 converging positions out of the 9converging positions are selectively placed in the machining region 91,so as to machine the object 90, while the remaining 7 convergingpositions are placed on the shielding member 40.

The laser beam outputted from the spatial light modulator 20 displayingeach of a plurality of holograms is converged by the converging opticalsystem 30 at M converging positions having a fixed number, N convergingpositions out of the M converging positions are selectively placed inthe machining region 91, and the object 90 is machined in thisembodiment as well. The remaining (M−N) converging positions are keptfrom being placed on the object 90. Since the number of laser beamconverging positions is fixed at M in each session, the laser beamirradiation energy at each converging position is substantially constantamong sessions, whereby fluctuations in machining can be suppressedamong sessions.

While the mover 60 moves the object 90, the spatial light modulator 20can display a hologram corresponding to the amount of movement in thisembodiment. Though the diffraction angle of the laser beam in thespatial light modulator 20 is limited because of the fact that the pixelpitch of the spatial light modulator 20 is fixed, this embodiment canmachine the wide machining region 91 by moving the object 90.

This embodiment may move the object 90 with respect to the lasermachining device 5 or the laser machining device 5 with respect to theobject 9. The mirrors 13, 14, spatial light modulator 20, convergingoptical system 30, and shielding member 40 in the laser machining device5 may be moved perpendicular to the optical axis of the convergingoptical system 30.

Sixth Embodiment

The sixth embodiment of the laser machining device and method inaccordance with the present invention will now be explained. The sixthembodiment differs from the first to fifth embodiments in that the unitof converging light and machining is a pattern having a fixed areainstead of a dot. The term “pattern having a fixed area” is meant toencompass lines as well. The sixth embodiment is basically the same asthe above-mentioned first to fifth embodiments except that the unit ofconverging light and machining is a pattern having a fixed area insteadof a dot, and thus will be explained in brief in the following mainly interms of its differences from the first to fifth embodiments.

Structure of the Laser Machining Device 1

The overall structure of the laser machining device 1 in accordance withthe sixth embodiment is substantially the same as that illustrated inFIG. 1. However, they differ from each other in terms of the function ofthe controller 22. The controller 22 in accordance with the sixthembodiment causes the spatial light modulator 20 to display a pluralityof holograms sequentially. Then, the controller 22 causes the convergingoptical system 30 to converge the laser beam outputted from the spatiallight modulator 20 displaying each of the plurality of holograms into aconverging region having an area X, which is a pattern having apredetermined area, selectively places a converging region having anarea Y out of the converging region having the area X in the machiningregion 91, and machines the object 90. Here, X is a positive number, andY is a positive number not greater than X. The machining region 91 wherethe above-mentioned converging region having an area Y is placedincludes not only the front face of the object 90 but also the insidethereof.

Laser Machining Method, Corresponding to the First Mode of the FirstEmbodiment

The above-mentioned description in the first mode of the laser machiningdevice in accordance with the first embodiment also applies to the sixthembodiment. FIG. 30 is a diagram for explaining this matter. FIG. 30( a)illustrates how the laser beam irradiates a converging region (patternh) having an area Y1 within the machining region 91 in order to machineletter “H”. FIG. 30( b) illustrates how the laser beam irradiates aconverging region (pattern p) having an area Y2 within the machiningregion 91 in order to machine letter “P” and a converging region(pattern p1) having an area (X−Y2) on the shielding member 40. FIG. 30(c) illustrates how the laser beam irradiates a converging region(pattern k) having an area Y3 within the machining region 91 in order tomachine letter “K” and a converging region (pattern k1) having an area(X−Y3) on the shielding member 40. Y1, Y2, and Y3 are examples of areas(area Y in the claims) of parts selectively placed in the machiningregion 91 and have the relationship of Y1>Y2>Y3 in terms of magnitude.The relationship of Y1, Y2, and Y3 can more easily be understood inconnection with the above-mentioned first embodiment if the areas Y1,Y2, and Y3 are assumed to be those of 12, 11, and 10 dots, respectively,for example.

That is, the laser beam outputted from the spatial light modulator 20sequentially displaying respective holograms corresponding to “H”, “P”,and “K” are converged by the converging optical system 30 into theconverging region having a fixed area of X. When machining letter “H”,the whole converging region having an area X is selectively placed inthe machining region 91, so as to machine the object 90 (i.e., X=Y1;FIG. 30( a)). When machining letter “P”, a converging region having anarea Y2 out of the converging region having the area X is selectivelyplaced in the machining region 91, so as to machine the object 90, whilea converging region having the remaining area (X−Y2) is selectivelyplaced on the shielding member 40 (FIG. 30( b)). When machining letter“K”, a converging region having an area Y3 out of the converging regionhaving the area X is selectively placed in the machining region 91, soas to machine the object 90, while a converging region having theremaining area (X−Y3) is selectively placed on the shielding member 40(FIG. 30( c)).

In FIG. 30, the maximum area Z of the converging region for machiningthe part of letter “H” (the part that requires the largest convergingregion area for machining among letters “H”, “P”, and “K” andcorresponds to the “predetermined part” in the claims) in the object 90equals Y1, which is identical to the total area X of the convergingregion of the laser beam. Here, Z is an integer.

Even when machining letters “H”, “P”, and “K” one by one in this order,the total area of the laser beam converging region is fixed at Xregardless of the letters, so that the laser beam irradiation energy ateach converging position is substantially constant among the letters,whereby fluctuations in machining can be suppressed independently of theletters.

Corresponding to the Other Items of the First to Fifth Embodiments

The foregoing explains that matters similar to those in the first modeof the laser machining method in accordance with the first embodimentcan be said in the sixth embodiment while taking account of the factthat the unit of converging light and machining is a pattern having afixed area instead of a dot. In view of the foregoing explanation, oneskilled in the art will easily understand that matters similar to theother items of the first embodiment, i.e., the first to fourth modes ofthe laser machining method in accordance with the first embodiment, thehologram producing method, and the hologram modifying method, can besaid in the sixth embodiment while taking account of the fact that theunit of converging light and machining is a pattern having a fixed areainstead of a dot. Also, in view of the foregoing explanation, matterssimilar to the second to fourth embodiments, the other modes of thefourth embodiment, and the fifth embodiment can be said in the sixthembodiment while taking account of the fact that the unit of converginglight and machining is a pattern having a fixed area instead of a dot.

For easier understanding, it is preferred to replace “M” with “X”, “N”with “Y”, “L” with “Z”, “M converging regions having a fixed number”with “a converging region having a fixed area X”, “N convergingpositions out of the M converging positions” with “a converging regionhaving an area Y out of the converging region having an area X”,“maximum number L of converging positions” with “maximum area Z of theconverging region”, and “(M−N) converging positions out of the Mconverging positions excluding the N converging positions to be placedin the machining region 91” with “a converging region having an area(X−Y) out of the converging region having an area X excluding theconverging region having an area Y to be placed in the machining region91” in the explanations of the first to fifth embodiments.

Modified Examples

Without being restricted to the above-mentioned embodiments, the presentinvention can be modified in various ways. For example, each of thesecond to fifth embodiments may employ the first to third modes ofwriting holograms into the spatial light modulator 20 explained withreference to FIGS. 2 to 4 in the first embodiment and the first tofourth modes of placing converging positions at the time of machining ineach session explained with reference to FIGS. 6 to 9, 24, and 25 in thefirst embodiment.

As with the fifth embodiment, each of the second to fourth embodimentsmay make the mover relatively move the object 90, while causing thespatial light modulator 20 to display a plurality of hologramssequentially.

Two or more of the structure comprising the shielding member 40 in thefirst embodiment, the structure comprising the 4f optical system 50 andshielding member 53 in the second embodiment, the structure comprisingthe 4f optical system 50 and mirror 54 in the third embodiment, and thestructure of placing the unnecessary (M−N) converging positions into aregion on the outside of the machining region 91 in the fourthembodiment may be used in combination.

All these modifications are applicable to the sixth embodiment as amatter of course. That is, the unit of converging light and machiningmay be a pattern having a fixed area instead of a dot in the foregoingmodified examples.

Example 1

A case initially machining at 2 converging positions and then at 4converging positions will be assumed here. A comparative exampleinitially sets the total number of converging positions to 2 and then to4. By contrast, as illustrated in FIG. 18, Example 1 initially places 2converging positions in the machining region 91 and 3 convergingpositions in a shielding region 92, and then 4 converging positions inthe machining region 91 and 1 converging position in the shieldingregion 92.

FIG. 19 is a chart listing laser beam intensities at respectiveconverging positions in the comparative example. It can be seen that thelaser beam intensity for machining varies between the case of machiningat 2 points and the case of machining at 4 points (e.g., 2200 nW and1100 nW at point 1). Since the light intensity varies, uniform machiningis difficult. FIG. 20 is a chart listing laser beam intensities atrespective converging positions in Example 1. The laser beam intensityat each converging position is found to be substantially constant(within the range of 905 nW to 920 nW) in Example 1, since the totalnumber of converging positions is fixed at 5 even when the number ofconverging positions varies in the machining region 91.

Example 2

Example 2 is carried out under totally the same condition as Example 1mentioned above but differs therefrom in that the unit of converginglight and machining is a pattern having a fixed area instead of a dot.That is, as illustrated in FIG. 31, Example 2 initially employs a linearpattern A having an area Y4 as a converging region in the machiningregion 91 and a pattern B having an area (X−Y4) as a converging regionin the shielding region 92 (FIG. 31( a)). Subsequently employed are alinear pattern C having an area Y5 as a converging region in themachining region 91 and a pattern D having an area (X−Y5) as aconverging region in the shielding region 92 (FIG. 31( b)). Here, Y4 andY5 are examples of areas (area Y in the claims) of parts selectivelyplaced in the machining region 91 and have the relationship of Y4<Y5 interms of magnitude. The relationship of Y4 and Y5 can more easily beunderstood in connection with the above-mentioned Example 1 if the areasY4 and Y5 are assumed to be areas of 2 and 4 dots, respectively, forexample. X is the total area of the laser beam converging region (areaof 5 dots in the above-mentioned example) as mentioned above, while thepattern B having an area. (X−Y4) and the pattern D having an area (X−Y5)may be in any forms.

FIG. 32 is a chart listing laser beam intensities in respectiveconverging regions in Example 2. The laser beam intensity is found to besubstantially constant (within the range of 910 nW to 920 nW) among theconverging regions in Example 2, since the total area of convergingregions is fixed at X even when the area of the converging region variesin the machining region 91.

Example 3

Irradiating the inside of glass as an object to be machined with afemtosecond laser beam can change its refractive index. Applying thistechnique can form optical waveguides, three-dimensional opticalcircuits, and the like within glass. When machined in a multipointscheme as mentioned above, an optical waveguide or three-dimensionaloptical circuit can be formed at a high speed within glass. However, therefractive index change in glass varies depending on the intensity ofthe femtosecond laser beam.

For example, assume a case where Y-branched optical waveguidesillustrated in FIG. 21 are formed. The object 90 in this case is glassin which optical waveguides 93 to 95 shaped like a Y branch are formedby irradiation with a laser beam.

As illustrated in FIG. 22, a comparative example using no spatial lightmodulator sequentially forms the optical waveguides 93, 94 (FIG. 22(a)), and then the optical waveguide 95 (FIG. 22( b)). This comparativeexample machines the optical waveguides one by one and thus takes a longmachining time.

Moving the object as in the fifth embodiment enables high-speed formingbut changes the intensity between before and after branching, wherebythe refractive index changes at the branching point. For evading this,the quantity of incident light is required be adjusted between beforeand after branching.

In the example corresponding to the above-mentioned fifth embodiment, 2points are always reproduced as illustrated in FIG. 23, so that thelaser beam intensity is substantially constant at each convergingposition. Therefore, Y-branched optical waveguides can be produced at ahigh speed with a high precision. In Example 3 explained in theforegoing, the unit of converging light and machining may be a patternhaving a fixed area instead of a dot as a matter of course. In thiscase, each circle in FIG. 23 refers to a pattern having a predeterminedarea.

INDUSTRIAL APPLICABILITY

A device and method are provided, which can easily keep the energy of alaser beam irradiating each converging position substantially constanteven when the number of laser beam converging positions in a machiningregion or the area of laser beam converging regions in the machiningregion varies.

1-48. (canceled) 49: A light irradiation device for irradiatingconverged light with an object, the device comprising: a light sourcefor outputting a light; a phase-modulating spatial light modulator forinputting the light outputted from the light source, displaying ahologram modulating a phase of the light at each of a plurality ofpixels arranged two-dimensionally, and outputting the phase-modulatedlight; a converging optical system disposed downstream of the spatiallight modulator; and a controller for causing the spatial lightmodulator to display a hologram such that the light outputted from thespatial light modulator is converged at a plurality of convergingpositions by the converging optical system, wherein the controllercauses the spatial light modulator to display a first hologram andperforms a feedback of the first hologram so as to modify the firsthologram, and wherein the modifying of the first hologram is performedby measuring intensity of the light converged at each of the convergingpositions, producing a second hologram by reproducing the first hologramusing Iterative Fourier Transformation on the basis of the intensity atany reference point of each of the converging positions, and displayingthe second hologram on the spatial light modulator. 50: The lightirradiation device according to claim 49, wherein the production of thesecond hologram is performed by altering amplitude of the light to bereproduced at each of the converging positions in accordance with theintensity at the reference point. 51: The light irradiation deviceaccording to claim 50, wherein the alteration in the amplitude of thelight to be reproduced at each of the converging positions is performedon the basis of a ratio of the intensity at the reference point to theintensity at each of the converging positions. 52: A light irradiationmethod for irradiating converged light with an object, the method using:a light source for outputting a light; a phase-modulating spatial lightmodulator for inputting the light outputted from the light source,displaying a hologram modulating a phase of the light at each of aplurality of pixels arranged two-dimensionally, and outputting thephase-modulated light; a converging optical system disposed downstreamof the spatial light modulator; and a controller for causing the spatiallight modulator to display a hologram such that the light outputted fromthe spatial light modulator is converged at a plurality of convergingpositions by the converging optical system, wherein the controllercauses the spatial light modulator to display a first hologram andperforms a feedback of the first hologram so as to modify the firsthologram, and wherein the modifying of the first hologram is performedby measuring intensity of the light converged at each of the convergingpositions, producing a second hologram by reproducing the first hologramusing Iterative Fourier Transformation on the basis of the intensity atany reference point of each of the converging positions, and displayingthe second hologram on the spatial light modulator. 53: The lightirradiation method according to claim 52, wherein the production of thesecond hologram is performed by altering amplitude of the light to bereproduced at each of the converging positions in accordance with theintensity at the reference point. 54: The light irradiation methodaccording to claim 53, wherein the alteration in the amplitude of thelight to be reproduced at each of the converging positions is performedon the basis of a ratio of the intensity at the reference point to theintensity at each of the converging positions.